1. Sex reversal studies and the effect of various steroid hormones in fish. No clearcut sex reversal has been observed after steroid treatment. 2. Analysis of clonal hyperdiploid CD+B cells in mice. The finding that IL-10 is increased in clones of CD5+B cells which in many respects are malignant, offers the possibility that anti-IL-10 may prevent the development of these clones and therefore be useful in the treatment of CLL. The hyperdiploid CD5+B cells are not only a model for such autoimmune diseases as rheumatoid arthritis and Sjogren's syndrome, they are very similar to the malignant cell in virtually all chronic lymphocytic leukemias. In all of these states, immunosuppression of normal B cell function is observed. The immunosuppression observed may be due to the IL- 10 which is produced. 3. Post and prenatal diagnosis of chromosomal aberrations in man. 4. Cytotaxonomic studies of the genus Macropodus and Trichogaster.